XPost: comp.lang.scheme
Matthew Danish wrote:
If you want to have some fun, why not write a nice higher-order function
to do:
(defun silly-loop (string &optional (increment 1) (final-char nil))
(loop for n from 0 by increment
for char across string
until (eql char final-char)
collect char into char-bag
sum n into sum
finally (return (values char-bag sum n))))
Try to make it half as readable. And as efficient.
Gauche Scheme
(use gauche.sequence) ;; map [generic]
(define (silly str :optional (incr 1) (ender #f))
(let@ (0 n sum)
(values
(map (^(char) (inc! sum n) (inc! n incr) char)
(if ender
(car (string-split str ender))
str))
sum n)))
(silly "catch" 37 #\h)
===>
(#\c #\a #\t #\c)
222
148
(silly "catch")
===>
(#\c #\a #\t #\c #\h)
10
5
Given:
(define-syntax let@-aux
(syntax-rules ()
[(let@-aux (0 var ...) (pairs ...) stuff)
(let@-aux () (pairs ... (var 0) ...) stuff)]
[(let@-aux ('() var ...) (pairs ...) stuff)
(let@-aux () (pairs ... (var '()) ...) stuff)]
[(let@-aux (var val more ...) (pairs ...) stuff)
(let@-aux (more ...) (pairs ... (var val)) stuff)]
[(let@-aux (var) pairs stuff)
(let@-aux (var '()) pairs stuff)]
[(let@-aux () ((var val) ...) (stuff ...))
(let* ((var val) ...) stuff ...)]))
(define-syntax let@
(syntax-rules ()
[(let@ things stuff ...)
(let@-aux things () (stuff ...))]))
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